[IshKebab]

There's this: https://rust-lang.github.io/fls/

But I think the lack of a formal specification is really not as big a deal as it's made out to be. It's one of those "think of a technical reason to justify a decision I've already made" excuses.

Obviously it would be great if Rust does get a full formal specification but I think avoiding it because it doesn't is just silly. C++ has a formal specification... which frequently has bugs and ambiguities. They aren't magically right and either way you're going to need to do a lot of non-formal testing as well as formal verification if you want confidence in a design.

This is true even for domains where formal verification is routine like SystemVerilog. I've seen designs pass formal but fail in simulation or vice versa due to subtle differences in the semantics. (Hopefully that can't happen for Rust but you get the point.)